Lithium greases



Patented July 2, 1946 LITHIUM GREASES Elvln B. Lien, Berkeley, Calif.,asaignor to Union Oil Company of California, Los Angeles, Calit, acorporation of California No Drawing. Application October 17, 1942,

Serial No. 462,413

13 Claims. 1

-This invention relates to lubricating greases, and the principal objectthereof is to p odu a stable lubricating grease tree from tendency tobleed" and to increased starting and running torque at low temperatures,and which is at the same time both water-resistant and stable totemperature fluctuations and pressure changes.

Primarily, the invention resides in a lithium soap grease which isrendered particularly suitable for extremely low temperature use,wherein the low temperature. properties are imparted through thepresence of a small proportion, e. g. 5%, of a so-called unsaponifiableoil obtained as a by-product from the production of soaps from acidicmaterialsproduced by oxidation of highly parafflm'c petroleumlubricating oil. Also, the lithium soap grease produced under thisinvention is rendered particularly stable against leakage of oil ortendency to bleed or weep. Furtherinore, such products are found to beappreciably improved in physical appearance in that they are unusuallyclear and brilliant in comparison with greases not containing theunsaponifiable oil.

The lithium soap used in the grease may be prepared in any known orpreferred manner from any appropriate fatty acid or other soap-makingacidic material suitable for grease manufacture.

For example, asuitable grease may be made from lithium stearate which isproduced in any appropriate manner from commercial stearic acid, such asby reacting lithium carbonate or other suitable lithium base withstearicacid. Similarly, other fatty acids such as oleic acid, palmiticacid andthe like or mixtures of these acids may be used according to wellunderstood soapmaking procedure. n Thus, both animal and vegetable fattyacid may be employed.

These lithium soaps may be employed in suit-.

able mineral lubricating oils in varying proportions according to theparticular type of grease desired. Normally, the stiffer the greasedesired, the greater the soap proportions. Whereas, a

I thin grease might contain only 1% or 2% 0! the soap, heavier-bodiedgreases will contain from 4% or 5% of soap up to 10% or 15% or any otherdesired proportion. Such greases have been described in patents. issuedto Clarence E. Earle Nos. 2,274,673, 2,274,674, 2,274,675 and 2,274,676,I

and various acidic materials appropriate therefor are indicated in thosepatents. In addition it may be desirable for some uses to use otheracidic materials such as naphthenic acids derived from petroleum wherebylithium naphthenates are produced. It may also be desirable for somepur- 2 i poses to employ synthetic acids produced by oxidation oflubricating oils, or the sulfonic acids obtained as a. by-product in themanufacture of white oils.

The present improvement renders greases of this type thoroughly stable,especially for low temperature uses such as for airplane lubrication,and protects them against a tendency to leak or "bleed some of the oil,especially where it is important to use low viscosity lubricating oils.This tendency is controlled or completely overcome by the employmenttherein of a small percentage, such as 5%, of the indicatedunsaponiflable oil or oily material which is recovered in connectionwith the production of metal soaps from the oxidation products of themodern highly parafilnic lubricating oils such as those which areproduced by solvent extraction of paraffin about 50 lbs. and 200 lbs. Atypicaloperation is to air-blow at a temperature of about 320 F. and

under a pressure of lbs. gage. Air blowing is carried on for a, time toproduce commercially maximum oxidation or other substantial degree ofoxidation. The oxidation batch which then.

contains substantial amounts of acidic materials, as indicated by atypical saponification value of 80, is then reacted with sodiumhydroxide, or other suitable base at a temperature of 250 F. and apressure of 60 lbs. per square inch, to form the desired sodium soap orother desired metal salt. Separation of the unsaponifiable oil isrealized by mixing the sodium soap and oil with a quantity of water, e.g. 25% water, heating the batch to around 180 F. to 200 F., agitating,and allowing the whole to settle. The soap layer settles to the bottomleaving an emulsion layer in the middle and a relatively clearunsaponifiable oil ontop. The soap and emulsion layersareeasilyseparated from-the unsaponifled oils which "consist principally ofunoxidized hydrocarbons,

It has been discovered that when minor proportions or this oil are usedin the lubricating oil employed in the grease production, an otherwisepresent tendency of the grease to bleed out some of the oil is overcome.This function is especially desirable where low viscosity oils, such astransformer oils or very light lubricating oils are employed for thegrease production. In addition to reducing this sweating tendency, thedescribed unsaponifiable oil also imparts appreciable physicaldifierence in that the product containing the unsaponifiable oil isclearer and almost transparent, as distinguished from a grease Theamount of saponifiable oil may vary from the indicated For example, aslittle as about 2% is efi'ective in lowering torque, reducing bleedingof oil, and rendering the product I clearer. Again, larger proportionssuch as 6% or 30 improve compatibilty.

8% may be introduced with increase in the desirable effects, up to anunsaponifiable oil content of about 10%, beyond which-there does notappear to be a constantly'increasing appreciable improvement. However,at least for some uses, it

-is possible to replace all of the lubricating oil or of mixed base, asdesired, and obviously, the

viscosity .of the oil will vary with the grease required.

In connection with avoidance of torque increase at low temperaturestests were made with a test shaft rotating in a'packed bearing and undera constant force, using greases made with transformer oil, as in thefollowing table:

Composition Grease T Sfeconds Trans. em or one 0mm, Lithium 5; protation on stearate on Percent Percent P F.

5.7 None 67 1,300 5.7 5.0 67 430 0.0 None -55 1,000 9.0 5.0 -s5 120 Thisshows a reduction in torque to about onethird where substituting 5%unsaponifiable' oil in same A to produce sample B and a reduction toabout-one-eight where making a similar substitution in sample!) (wherethe soap content is greater) to produce sample D. In zaddition toemploying the described unsaponifiable oil for the purposes indicated,it is SAE grades from inasmuch as there is sometimes a tendency forlithium greases to darken substantially after manufacture. A verydesirable material for this purpose has been found to be phenyl alphanaphl thylamine. An adequate proportion is about 0.2%

of the grease, but this may be varied according to the extent of controldesired from perhaps as little as 0.05% to perhaps as much as 1.0%,although greater proportions than 1.0% can be 19 employed, if desired,to further increase the oxidation resistance of the grease. Anothersuitable anti-oxidant is p-phenylene diamine. Also,

other high boiling point 'arylamines and other inhibitorsmay-be'emplo'yed in somewhat similar proportions.

In addition to employing lithium soaps, such as lithium stearate, thereare occasional instances where it seems desirable to add smallerproportions of other soaps. For example, about 20 to 2% of calciumstearate, sodium stearate, magnesium stearate, or especially aluminumstearate,

or soap or similar acid, may be added to a grease containing in theorder of 10% of lithium stearate. Similarly, small proportions of theseadditional soaps maybe addedto greases containing either less or morelithium stearate, such as to greases containing 4% or 5% of lithiumstearate or other lithium soap. The purpose of these.

additions, when desirable to employ them, is to Variations in theproduct and in the method of its production will be apparent to thoseskilled in the art. For example, the compatibility-improving soaps maybe prepared from any acid 36 previously mentioned for 1ithium=soaps. I

v I claim: v 1 I v 1. A lubricating grease comprising mineral oil,

a minor proportion of lithium soap, and a minor proportion ofunsaponifiable oil obtained from 40 the recovery of synthetic acidsproduced by the oxidation of lubricating oil fractions. 2. A lubricantcomprising mineral lubricating oil, about 1% of lithium soap, and aminor proportion of unsaponiflable oil obtained as a byproduct afterrecovery of synthetic acids produced bythe oxidation of a petroleumlubricatin oil fraction.

3. A lubricant comprising a petroleum fraction of lubricating viscosity,a minor proportion of lithium-soap to thicken the oil, and a minorflcient to reduce tendency to increase torque at sub-normaltemperatures.

4. A lubricant according to claim 3 wherein the unsaponifiable oil ispresent in excess of about 2% of the total composition. I so 5. Alubricant according to claim 3 wherein the soap is present in proportionin excess of about 1% and the unsaponiflable oil is present in excess ofabout 2%.

6. A lubricating grease comprising a mineral 5 oil fraction havinglubricating viscosity, a minor proportion of lithium soap to thicken theoil, and a minor proportion uflicient to prevent bleeding oiunsaponiflable oil obtained after separation of synthetic acids producedby' the oxidation 01' a refined petroleumfraction.

'7. A lubricant comprising a petroleum frac tion of lubricatingviscosity, 9. minor proportion between about 1% and 25% of lithium soap,and I a minor proportion between about 2% and 1 sometimes desirable toadd an oxidation inhibitor, of unsaponifiable oil obtained afterseparation of synthetic acids produced by the oxidation of re- 10. Alubricant according to claim 3 contain ing phenyl alpha naphthyiamine ina minor proportion sufllcient to act as an oxidation inhibitor. 11. Alubricantaccording to claim 3 containing a minor proportion suflicientto act as a compatibility agent of a soap 0! the class consistin oi!calcium, sodium, magnesium and aluminum soaps. 4 v

12. A lubricant according to claim 3 containing a high boiling oint arylamine in minor proportion suflicient to act as an oxidation inhibitor.

13. A lubricant according to claim 2 wherein the unsaponiflable oil ispresent in proportion suiiicient to reduce tendency to increased torqueat subnormal temperatures.

- ELVIN 28. HEN.

